Conventional waste water disposal systems in aircraft kitchens have the disadvantage that a separate conduit is necessary in order to blow out the waste water from the aircraft body into the environment. The connection of a hand wash basin in the toilet to the outside of the aircraft is accomplished, either directly without the intermediary of a discharge valve or by using such a discharge valve, also referred to as drain stop valve.
The just described waste water discharge systems in commercial aircraft treat waste water from kitchen sinks and waste water from hand wash basins in the toilet in the same manner by discharging all the waste water to the environment through which the aircraft is flying. However, sewage from toilet basins and water for flushing toilets in an aircraft is collected in a sewage water tank. Conventionally, the conveyance of the sewage to the tank takes place by applying reduced pressure to the sewage collection tank.
Where drain stop valves are not used, cabin air continuously escapes through the drainage conduits because the air pressure within the aircraft is higher than the pressure of the environment through which the aircraft is flying. Where such a drain stop valve is used, a liquid column accumulates on a spring biased flap. When the liquid column reaches a weight that exceeds the biasing force of the spring, the valve is briefly opened, whereby the waste water is discharged as long as the flap remains open. Depending on the type of construction, such a drain stop valve has a diameter of about 200 mm. This required valve dimension imposes its limitation on the structural features of the location where such valves can be installed. Especially, when available space is limited, for example, in an on-board kitchen, it may become necessary to install the valve in a space that would otherwise be available as a storage space. Such storage space may be even large enough to take up half of a serving cart.
As a result, conventional waste water disposal systems in an aircraft require a high installation effort and expense involving high material costs as well as a substantial installation effort. Further, the conventional dimensions for the structural components of such systems reduce the useful effect or capacity of such conventional components.